MINIMIZATION OF ELECTRIC CONSUMPTION BY A FREQUENCY-REGULATED INDUCTION MOTOR IN START-BRAKING REGIMES

Abstract

Purpuse. To minimize the total energy consumption in start-braking regimes of a three-phase frequency-regulated induction motor loaded with a constant static moment, as well as to take into account the effect of iron power losses of this motor on electrical losses of power and energy in its stator winding. Metodology. Based on the established similarity of mathematical dependences for calculating the electrical component of power losses in the stator winding of this motor, caused by the influence of iron power losses of the motor or the application of an additional fictitious static moment to it, the analytical dependences were refined to determine the total power and energy consumed by the motor in steady-state and start-braking regimes. Using the methods of calculus of variations and simulation, the form of energy-saving tachograms was determined, which ensure, in start-braking regimes, the minimization of the total power consumption of this motor, loaded with a constant static torque. Results. Analytical calculated dependencies are proposed for determining the energy consumption in the start-braking regimes of a frequency-regulated squirrel-cage induction motor loaded with a constant static moment, for various types of trajectories of speed change. Analytical dependencies are obtained, by means of which a quantitative assessment of the influence of iron power losses of the investigated motor on the values of the stator current modulus and electrical power and energy losses in its stator winding is carried out under steady-state and start-braking regimes. With regard to the constant load of this motor, the minimization of the active energy consumed by it in the start and braking regimes has been performed. For start-braking regimes with the proposed quasi-optimal and known types of tachograms, the optimal durations of acceleration and deceleration times, at which the consumption of active energy by the induction motor is minimal. Originality. The "U"-shaped form of dependences of the total consumed energy by the frequency-regulated induction motor on the durations of the acceleration and deceleration times has been established. For start-braking regimes, the minimization of the total energy consumed by this motor was carried out and quantified, achieved through the use of energy-saving tachograms and optimal durations of acceleration and deceleration times. Practical value. For start and braking regimes, a quantitative assessment of transient electromechanical and energy processes in a frequency-regulated short-circuited induction motor for driving vertical slab rolls was carried out and the expected annual saving of energy consumed by this motor in these regimes, achieved from the use of the proposed energy-saving tachograms, was determined. Figures 4, tables 5, references 19.